CAREER: Using Three-Dimensional Confocal Rheology to Measure Shear Induced Microstructural Deformations in Colloidal Glasses

复杂流体是由熟悉的成分产生的具有独特性质的迷人材料。例如，乳液和泡沫，如沙拉酱和座垫，都是由液体和空气等简单材料组成的，但它们的材料特性仍然是人们非常感兴趣的话题。这个早期教师职业奖的目标是通过使用乳剂（一种特别有趣的复杂流体）来获得对玻璃化转变的更广泛的理解。乳剂是非常小的液滴的集合，分散在另一种流体中，非常类似于原子和分子的行为。然而，由于它们的尺寸相对较大，与原子相比，它们的位置和运动的直接和实时测量是可以实现的。玻璃化转变描述了当液体突然冷却时导致其凝固的一种转变。快速冷却迫使材料保持无序状态，同时以某种方式变成固体。值得注意的是，当这些液滴紧密地聚集在一起时，它们会经历一个过渡，所有的液滴都会堵塞，从而形成一种结构上与窗户玻璃非常相似的材料。通过同时对由乳化液液滴组成的玻璃进行变形和成像，可以直接测量有关机械性能的信息，包括每个液滴所受的力。这些信息将为玻璃化转变的起源提供关键的见解，并将有助于描述这些复杂材料的理论模型的发展。PI发起的一个主要教育组成部分是中大西洋软物质研讨会（MASM）的发展。该研讨会为该地区的研究人员提供了一个理想的论坛，他们的兴趣在于传统学科的界面。讲习班自然也有助于青年科学家的职业发展，使他们熟悉当地的学术和工业研究界。【技术摘要】这项早期教师职业奖的研究重点是发展在体积和微观尺度上精确控制和确定软玻璃固体力学性能的独特能力。胶体悬浮液（乳剂）系统被用来制造材料，使其经历类似于各种凝聚态材料中的玻璃化转变的动力学停滞。是什么使实验方案中所描述的独特之处在于在直接高速三维成像过程中施加精确剪应力的方法的发展。该技术将允许系统在外部驱动和测量（流变学）的同时，在微观尺度上测量材料的动态和结构演变。为了开展这项拟议的研究，将两种成熟的软材料量化技术结合起来；共聚焦显微镜和体流变学。从更广泛的角度来看，胶体玻璃内部微观结构的测量将允许非晶材料微观理论的发展，这将提供实用和基本的见解。PI发起的一个主要外展组成部分是中大西洋软物质研讨会（MASM）的发展。该研讨会为该地区的研究人员提供了一个理想的论坛，他们的兴趣在于传统学科的界面。讲习班自然也有助于青年科学家的职业发展，使他们熟悉当地的学术和工业研究界。

Non-Technical AbstractComplex fluids are fascinating materials with unique properties that arise from familiar constituents. For example, emulsions and foams such as salad dressing and seat cushions are comprised of simple materials such as liquid and air, yet their material properties remain topics of overwhelming interest. The goal of this Early Faculty CAREER Award is to gain a broader understanding of the glass transition by using emulsions -- a particularly interesting complex fluid. Emulsions are collections of very small liquid droplets, dispersed within another fluid, that closely mimic the behavior of atoms and molecules. However, due to their relatively large size, direct and real-time measurements of their positions and motions are obtainable in contrast to their atomic counterparts. The glass transition describes a transition in liquids that leads to their solidification when they are abruptly cooled. Rapid cooling forces the material to remain disordered while somehow becoming a solid. Remarkably, when these fluid droplets are tightly packed together, they undergo a transition where all of the droplets jam up, resulting in a material that is structurally very similar to window glass. By simultaneously deforming and imaging a glass comprised of emulsion droplets information about the mechanical properties, including the force on each droplet, can be directly measured. This information will provide key insights into the origins of the glass transition and will aid in the development of theoretical models that describe these complex materials. A major educational component initiated by the PI is the development of the Mid Atlantic Soft Matter Workshop (MASM). This workshop provides an ideal forum for researchers within the region whose interests reside at the interface of conventional disciplines. The workshop also naturally assists in the career advancement of young scientists by acquainting them with the local academic and industrial research community. Technical AbstractThe research in this Early Faculty CAREER Award is focused on developing the unique ability to precisely control and determine the mechanical properties within soft glassy solids at the bulk and microscopic scales. A system of colloidal suspensions (emulsions) is utilized to create materials that undergo kinetic arrest similar to the glass transition in a variety of condensed materials. What makes the experimental program described in this proposal unique is the development of methods to impose precise shear stresses during direct high speed three dimensional imaging. This technology will allow the system to be externally driven and measured (rheology) while simultaneously measuring the dynamic and structural evolution of the material at the microscale. To carry out this proposed research, two well established techniques for quantifying soft materials are combined; confocal microscopy and bulk rheology. From a broader perspective, measurements of the microstructure within colloidal glasses will allow for the development of microscopic theories of amorphous materials that will provide both practical and fundamental insights. A major outreach component initiated by the PI is the development of the Mid Atlantic Soft Matter Workshop (MASM). This workshop provides an ideal forum for researchers within the region whose interests reside at the interface of conventional disciplines. The workshop also naturally assists in the career advancement of young scientists by acquainting them with the local academic and industrial research community.